Nonassociative learning: Learning involving exposure usually to a single event, and that is presumed not to reflect learning of a relationship between multiple events.
Habituation Ð A decline in responsiveness to repeated stimulation arising from a central change in the organism.
Dishabituation Ð The recovery of responsiveness to a stimulus that has undergone habituation training due to the recent occurrence of an extraneous stimulus.
Sensitization Ð The increase in responsiveness to a stimulus that has not undergone habituation training thought to arise from a general arousal process.
1. The potentiated startle response procedure nicely illustrates the concept. In this situation, startle responding to the 1st presentation of an auditory stimulus (e.g., tone) is assessed in two groups of rats. In the first group, the control group, the baseline level of responding is determined by simply presenting the tone to the rats and measuring the startle response. In the second group, experimental group, startle responding to the tone is assessed some time after presentation of some sensitizing event (like electric foot shock). The startle response in this group is increased relative to that seen in the control group.
2. Whitlow (1975) demonstrated that it is possible for an extraneous event to dishabituate, but not sensitize, responding to another stimulus. On these grounds, he inferred that dishabituation and sensitization, although both referring to increases in responding, have separate underlying mechanisms. If the two phenomena had a common underlying mechanisms, then whenever a stimulus could serve as a dishabituator, it should also act as a sensitizer (and visa versa). His experiment showed that this was not the case.